This invention relates generally to a control mechanism usable on tractors to control the operation of hydraulically powered mechanisms and, more particularly, to a control device operably interconnecting two separate hydraulic functions to effect the automatic movement of one function in response to the selective movement of the other function.
With the advent of a hydraulically powered articulated tractor such as marketed by Ford New Holland, Inc. as the Model 276 Bidirectional.TM. tractor, it has been desirable to provide implements mounted thereon to accomplish harvesting and other farming functions through use of the tractor. Hydraulically powered implements such as a mounted mower conditioner provide great flexibility in the use of the Bidirectional.TM. tractor. One of the limitations on the use of such implements is the hydraulic flow capacity of the tractor. In some situations, the hydraulic pump can be inadequate to provide the necessary flow of hydraulic fluid to satisfy the simultaneous need for steering the articulated tractor, driving the operable components of the implement, and powering the movement of a component or components of the implement, such as a crop harvesting header.
The hydraulic control valve for the hydraulic system on the Bidirectional.TM. tractor is provided with four spools, each of which is equipped with a flow control to limit the flow of hydraulic fluid through the spool. The spool associated with the steering of the tractor has full priority over the other spools and control thereof is independent. The mounting of an implement such as a mower conditioner on a tractor requires a satisfactory flow of hydraulic fluid to a hydraulic motor powering the operation of the harvesting components of the implement header. These two hydraulic mechanisms require a significant flow of hydraulic fluid such that very little remains for lifting the header relative to the ground, particularly when the hydraulic cylinder which is operably powering the header lift mechanism requires a greater pressure than is normally needed to power the rotation of the hydraulic motor operably driving the components of the implement.
Under such conditions, a manipulation of the control for the spool to activate the header lift cylinders has limited success because of the continued flow of hydraulic fluid to the hydraulic motor. Since operation of the components of the crop harvesting header is normally not needed when the header is being raised into a transport position above the ground, it would be desirable to provide a control linkage operable to reduce the flow of hydraulic fluid to the hydraulic motor whenever the hydraulic lift cylinders are actuated to effect a lifting of the header relative to the ground.